Belt guiding means for suction boxes



March 26, 1963 E. J. JUSTUS ETAL 1 BELT GUIDING MEANS FOR SUCTION BOXES Filed Jan. 50. 1961 3 Sheets-Sheet 1 INVENTORJ [cgyar I fusfzz:

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. AT RNEYS March 26, 1963 E. J. JUSTUS ETAL 3,082,819

BELT GUIDING MEANS FOR SUCTION BOXES 5 Sheets-Sheet 2 Filed Jan. 50. 1961 IN V EN TORS [d rar f. Jujzus BY Penn (5 6 ran in March 26, 1963 E. J. JUSTUS ETAL 3,082,819

BELT GUIDING MEANS FOR SUCTION BOXES Filed Jan- 60, 1961 5 Sheets-Sheet 3 INVENTORS [ajyar ffzzslu:

I BY Penn 1': C [rarzz'n A ORNEYS United States Patent 3,082,819 Patented Mar. 26, 1953 [ice 3,682,819 BELT GUlDlNG MEANS FOR SUCTION EQXES Edgar J. Justus and Dennis C. Cronin, Beloit, Wis, assignors to Beloit Iron Works, Beioit, Wis, a corporation of Wisconsin Fiied Jan. 30, 1961, Ser. No. 85,664 8 Claims. (Cl. 162--34-) The present invention relates broadly to the paper making and related arts, and is more particularly concerned with new and improved means having especial utility in the guiding of a moving belt traveling in supporting contact with a forming wire over a suction box in the Fourdrinier type paper machine.

As is well known, the conventional Fourdrinier type paper machine comprises a looped traveling forming wire presenting a forming reach extending from a breast roll, at which the stock is flowed onto the wire, to a suc tion couch roll located approximately at the station at which the formed web is removed from the wire. Various de-watering devices are mounted beneath this reach of the forming wire, and one common dewatering device is known as a suction box and presents a flat perforate top to the bottom side of the wire. The interior of the suction box is exhausted to assist in drawing water from the web through the wire and through the perforations in the flat top of the suction box. The pressure differential which is thereby created tends to hold the traveling wire down against the stationary flat top of the suction box, resulting in increased wear on the wire.

Various means have been suggested for the purpose of avoiding wire wear caused by drawing the moving wire over fixed suction boxes, and vone known structure takes the form of a perforated moving belt with solid edges which is installed between the traveling Fourdrinier wire and the suction box covers. However. largely as a result of the inherent stiffness in the belt and pull thereon as the belt reverses its direction of travel, combined with suction forces on the belt, the belt will flex or whip upwardly at the oncoming side of the suction box. Numerous disadvantages result from this action. First, fiber formation is disrupted by the forces applied by the belt in its flexed state and by introducing air between the belt :and suction box top, causing uneven drainage. Second, the flexing often causes the belt to travel unevenly across the suction box cover, so that the belt is in efiect skewed, with the result that the belt edges may rub against the guides on the cover and cause belt damage. Third, both the belt and the suction box cover have perforations therein which periodically align themselves during travel of the belt over the cover. If the belt does not travel in a straight line path along the cover, the respective holes in the belt and cover do not align themselves and poor dewatering of the web results.

In addition, and also the cause of the last-named Ob. jection of uneven belt travel, is a difference in the relative peripheral lengths of the belt on opposite sides thereof resulting from unavoidable errors in belt manufacture. While a difference of of an inch in a belt having an inner circumferential length of fifteen feet may seem at first insignificant, the mere fact that one side is relatively longer than the other side causes the short side to lead and the long side to lag. This effect is cumulative during continuous belt travel, and ultimately the belt becomes skewed relative to the longitudinal centerline of the suction box top. Again, the drain perforations in the belt and cover become misaligned, resulting in poor dewatering and even a seizing of the belt to the cover.

The instant invention resides in a novel, simple and particularly effective arrangement for overcoming these difficulties. In accordance with the present teachings, the belt is guided during its travel about the suction box by first and second guide means, the first guide means presenting a curved surface abutting the oncoming side of the suction box and having a radius such that the belt is properly tensioned and smoothly transcends from the curved surface onto the suction box top without rising therefrom, and the second guide means presenting a lcurvate surface contoured to restrain or confine the belt or looped carrier band to a symmetrical shape so that the belt during travel conforms to its natural curvature in an untensioned state.

The first guide means, and which are particularly effective in eliminating the noted belt fiexure problem upon entry onto the suction box top, desirably take the form of a header member having a precisely contoured belt receiving surface. In most applications a header member is utilized at both the oncoming and off-running sides of the suction box, extend substantially entirely across the width of the belt, and are passed to supply fluid to perforations in the suction box cover to lubricate the underside of the belt during travel thereover. The radius of the belt receiving surface on the oncoming guide means is precisely controlled, since if the radius is too large the belt is unduly tensioned, whereas if the radius is too small the belt does not smoothly transcend or enter upon the suction box cover, with the result that the belt flexes in the manner earlier noted.

The second guide means, on the other hand, in an exemplary embodiment of the invention comprises an arcuate plate member suitably attached along the underside of the suction box and assures effective guidance and positioning of the belt so that each element of the belt travels through the same angular distance during one revolution. The second guide means can, however, be provided by one or more rolls or rod members within the belt loop and which also effectively confine the belt so that its shape constantly during each revolution is symmetrical and conforms to its natural curvature when in a relaxed or untensioned state. The second guide means if provided by roll or rod means within the belt loop may further be equipped with tension control capabilities by utilization of means for shifting the guide roll vertically or horizontally about the axis thereof. Other features of the first and second guide means will be noted in connection with the detailed description appearing hereinafter.

It is accordingly an important aim of the present invention to provide an improved paper machine, and more particularly, to provide novel means for guiding the moving belt traveling about a suction box in a Fourdrinier type paper machine.

Another object of this invention lies in the provision of guide members positioned at the oncoming and off-running sides of a suction box which effectively prevent flexing of the belt at the oncoming side to prevent disruption of fiber formation, belt damage and ineffective web dewatering.

Still another object of this invention is to provide guide means located generally beneath the suction box and which confine the belt to a symmetrical shape by a restraining action so that each element of the belt travels through the same angular distance during one revolution about the suction box.

A further object of the instant invention lies in the provision of a paper machine including a suction box receiving thereover an endless flexible belt or looped carrier in supporting contact with a traveling forming wire or drain band, and which paper machine embodies the improvement of first guide means providing a curved surface at the oncoming side of the suction box and having a radius such that the belt is properly tensioned and smoothly transcends onto the top of the suction box without rising therefrom, and second guide means within the loop of the endless belt and having a curvature such that the belt conforms substantially to its natural curvature in an untensioned state.

Other objects and advantages of the invention will become more apparent during the course of the following description, particularly when taken in connection with the accompanying drawings.

In the drawings, wherein like numerals designate like parts throughout the same:

FIGURE 1 is an essentially diagrammatic elevational view of a paper machine embodying web dewatering apparatus constructed in accordance with the principles of this invention;

FIGURE 2 is an enlarged view of the web dewatering apparatus of FIGURE 1, and showing more particularly first and second guide means connected thereto;

FIGURE 3 is an enlarged sectional fragmentary detail view taken substantially along the line "IIIIII of FIG- URE 2;

FIGURE 4 is a fragmentary detail end view of one form of first guide means to prevent belt flexing, and showing further therein means for supplying liquid from the interior of the guide means to conduit means on the underside of the suction box top to lubricate the belt traveling thereover;

FIGURE 5 is a fragmentary top plan view of the forming wire, supporting looped belt and suction box cover, and illustrating particularly proper alignment of perforations in the belt with perforations in the suction box cover when the belt is traveling properly thereover;

FIGURE 6 is a view similar to FIGURE 5, but showing misalignment of the belt and cover perforations when the belt is skewed as a result of the shorter side thereof leading the longer side;

FIGURE 7 is a fragmentary detail view, with parts thereof in section, and illustrating one manner of attaching the second guide means to the underside of the suction box; and

FIGURES 8, 9 and 10 are diagrammatic elevational views of other forms of web dewatering apparatus incorporating modifications to the first and second guide means therein.

Referring now to the drawings, there is shown in FIG- URE 1 a paper machine indicated generally by the reference numeral 10, and comprising a looped forming wire 11 trained over a breast roll 12, table rolls 13, suction box 14, couch roll 15, a turning roll 16, and return rolls 17. Stock is deposited on the upper wire run 11a from a head box 18 onto a forming board 19 in the region of the breast roll 12, and the stock is dewatered during its travel on the upper wire run 1111 to form a web W which is removed from the wire 11 by a pickup felt 29 urged against the web W by a suction pickup roll 21. A rotary belt 22 is driven by the forming wire 11 about the suct'ion box 14 and is guided during its travel by first guide means 23 and 24 and second guide means 25, the structural features of which will be later dealt with in detail.

The present invention is directed to guide means 2325 for preventing skewing of a rotary elastomeric belt 22 in association with a suction box in a Fourdrinier type paper machine, as is shown in FIGURE 1. The structural details of the suction box 14 and traveling belt 22 form no part of the instant invention, and only such details thereof are illustrated as are required for a clear understanding of the present invention. Accordingly, it will be appreciated that other moving belts and stationary suction boxes may be substituted in lieu of the structures shown, and other changes made to various other portions of the paper machine 10. As well, and as will be brought out in the descriptive material appearing hereinafter, the first guide means 23 and 24 and second guide means 25 are susceptible to numerous variations, and further, While in FIGURES l and 2 the rotary belt 22 is driven by the forming wire 11, one or more drive rolls can be utilized within the loop of the endless belt, and in such an arrange- 41- ment, the first guide means 23 and 24 assume a somewhat different contour in the lower portions thereof.

The illustrative form of suction box designated at 14 in FIGURE 2 comprises a generally rectangular troughlike body portion 30 having opposed side walls 31 and 32 integrally connected to a bottom wall 34, and removable end walls 33, one only of Which is shown. The open top of the suction box body portion 30 mounts thereon a cover member 35, the drain perforations and fluid supply passages of which will be later described in connection with succeeding views of the drawings.

T 0 provide an effective seal between the end walls 33 and the body portion 30 of the suction box 14, and to provide a convenient mounting of the end walls to the body portion, the side walls 31 and 32 and bottom wall 34 may mount thereon flange means 35 having bolt receiving openings 36a therein. Gasket means (not shown) are located between the flange means 36 and opposed end walls 33, and the end walls are equipped with mating openings for receiving bolt means or the like threaded into the openings 36a.

To rigidify the suction box 14 and to provide a supplemental mode of attachment of the cover 35 thereto each end wall 33 adjacent the upper end thereof has Welded or otherwise secured thereto longitudinally extending beam members 37 of a length generally coextensive with :the length of the end walls. Cooperating with the beam members 37 to conveniently support the cover 35 is a second pair of beam members 38, each having longitudinally spaced openings 38a therein threadably receiving screw means 39. The screw means 39 may be of the same character employed to attach the cover member 35 to fluid supply conduit means in a manner to be later hereinafter described. In any event, it may be seen that the plate member 35 has a plurality of mating countersunk openings 49 therein so that the heads of the screw means is recessed in the cover member 35. As well, as is shown in FIGURE 2, opposed side walls 31 and 32 of the suction box body portion 30 are recessed at the upper ends thereof to provide ledge means 31a and 32a to seat opposite sides of the cover member 35.

Further details of the cover member appear in FIG- URE 5, and upon reference thereto in conjunction with FIGURE 3 it may be observed that the flat plate-like cover member 35 is equipped with a plurality of transversely spaced rows of drainage openings or perforations 42 running and spaced longitudinally in the direction of wire travel indicated by the arrow 43. The perforations 42 open into the interior of the suction box 14, and conveniently the opposed end walls 33 of the box may be passaged at 33a to receive branch conduits 64a and 6412 connected as is shown diagrammatically to a main conduit leading to exhaust means in the form of a pump 44.

As is shown in the cut-out portion of FIGURE 5, the suction box top or cover 35 has land areas 45 intermediate the perforations 42 and providing a lubricant receiving surface whereby the traveling belt 22 is carried by a fluid film during travel along the suction box cover. The land areas 45 between the rows of perforations 42 are apertured as at 46 in countersunk configuration (to receive therein passaged attaching means 47 threadably connecting the cover member 35 to roof portion 50a of conduit means 50, further details of which will be later noted. The passages or perforations 46 extend from near the off-running edge of the suction box cover 35 to near the oncoming edge, and in common with the land areas 45 and perforations 42, extend longitudinally in the direction of wire travel.

There will be later described the structural features of the first guide means 23 and 24, which desirably also function as fluid supply headers to the conduit means 55 however, it should be emphasized at the present moment that water flows upwardly in and outwardly from the passaged attaching means 47 in generally the manner indicated by the arrows 48 in FIGURE 5. The water flows in the directions indicated along the land areas 45 and ultimately to the drain perforations 4-2. The flow as illustrated in FIGURE 5 is very slight and is controlled by the pressure of the belt 22 against the land areas 45, however, the flow is sufiicient to lubricate the rubber belt 21 and to prevent dragging thereof over the dry land areas 45, when belt skewing is prevented by the second guide means 25.

The belt 22 is provided with perforations or drainage holes 22a, as indicated in FIGURES 3 and 5, and said holes are so located in the traveling belt that they do not align themselves with the passages in the attaching screw means 4-7 communicating with the conduit means 50. In this way, water is not forced back up through the drainage holes 22a. Instead, the drainage holes periodically align themselves with the perforations 42 in the suction box cover 35. The bottom side of the belt 21 has, of course, a number of openings therein formed by the drainage holes 22w. Intermediate said drainage holes there are land areas 22b on the bottom side of the belt which cover the passages in the screw means 47. These belt land areas 22b are urged downwardly against the suction box land areas 45 by the pressure differential created by the suction box 14. For this reason, water is urged into the passaged screw means 47 under slight pressure to efiect continuous seepage of water between the faces of the land areas 22b and 45, this seepage being necessary to prevent the rubber belt 22 from wiping the land areas 45 dry, and thereby increasing the frictional drag. Preferably, the seepage of water is very slight so as not to overload the water removal system for the suction box 14.

The top side of the belt 22 is provided with a plurality of longitudinally spaced laterally extending grooves or channels 220, one of which is shown in FIGURE 3. Each such groove 22c is provided with one or more of the drainage holes 22a, which as earlier noted, periodically communicate with the perforations -42 in the suction box cover 35.

The conduit means se for supplying fluid through the passaged screw means 47 includes a roof portion "Ella threadably receiving the attachment means 47 and a channel portion Sllb welded or otherwise secured to the roof portion Ella. The conduit means are transversely spaced and longitudinally extending, and one mode of attaching the conduit means to the suction box wall structure is illustrated in FIGURE 4. As appears therein, the channel portion Stlb of each conduit member 5t may be seated upon transversely extending shelf members 51 suitably secured to opposed side walls 31 and 32 of the suction box 14. Further, at opposite ends of each conduit member and interiorly thereof there may be welded or otherwise attached an apertured bushing 56. Threadably received in the rigid bushinx 5c is passaged bolt means 57 having an opening 57a extending therethrough. Each bolt member 57 is threaded into the side walls 3 1 and 32 of the body portion of the suction box, as well as into the bushing 56. In this manner, the conduits 50 are firmly attached to the opposed side walls 31 and 32, provide support for the suction box cover 35, rigidify the cover, and provide an efiective fiuid supply means for the passaged threaded fasteners 47 connecting the cover 35 to the conduit members 50. As is now apparent, the passaged screw means 57 may take the same form as the screw means 3? and 47.

As appears in FIGURE 3, the suction box cover 35 adjacent opposite ends thereof may mount belt guide means 49, which may take the form of an angle member secured to the cover 35 by screw means 49a. The guide means 49 may be spaced along the length of the suction box cover 35 or run continuously therea-long, but in any event, the guide means 49' prevent excessive lateral shifting of the belt 22 during travel along the suction box cover 35.

It was noted in the introductory material hereto that largely as a result of the inherent stiffness in the belt 22 and pull thereon as the belt reverses its direction of travel, combined with suction forces on the belt, the belt will flex or whip upwardly at the oncoming side of the suction box 14 This action disrupts fiber formation by the forces applied to the belt in its flexed state and by introducing air between the belt and suction box top 35, causing uneven drainage. Also, the flexing often causes the belt to travel unevenly across the suction box cover, so that the belt in effect is skewed, with the result that the belt edges may rub against the guide means 49 and cause belt damage. In addition, it is essential for effective operation that the belt drainage perforations 22m and cover drain perforations 42 periodically align themselves during travel of the belt 22 over the cover. If the belt does not travel in a straight line path along the cover, the respective holes in the belt and cover do not align themselves and poor dewatering of the web W results. As well, if the belt becomes skewed relative to the suction box cover 35, the belt land areas 22b may locate themselves over the cover perforations 42, causing the belt to seize upon the cover 3 5.

In accordance with the present inventive concepts, belt flexing and the stated problems resulting therefrom are eliminated by provision of a first guide means 23' having a belt engaging surface 23a contoured or shaped from essentially the line of belt engagement (designated at x in FIGURE 4) to the line of entry of the belt onto the box structure (identified at y in the same view) such that the belt 22 is properly tensioned and smoothly transcends from the curved surface 23a onto the suction box top 35 without rising therefrom. The other first guide means Z-tat the off-running side of the suction box 14 is desirably identically shaped for substantially the same reasons, although it is at the oncoming side of the box that the entry problem exists, and accordingly, 9. somewhat differently shaped guide 24 may be utilized, as will be hereinafter noted.

Extensive investigations have demonstrated that the belt engaging surface 23a has a critical radius. Thus, if the radius is too large, an undue amount of tension is applied to the belt 22 and excessive belt drag over the cover 35 results. While too large a radius on the belt engaging surface 23a does not apparently interfere with attainment of proper entry onto the cover and is thereby effective to eliminate belt flexing, a radius too low for the surface 23a frequently produces belt flexing. In the latter case of too small a radius, there is not, on the other hand, apparently any undue tension forces applied to the belt 22'.

It has been noted that the critical radius for the belt engaging surface 23a extends from the points x and y in FlGURE 4, the latter point being seen to be somewhat upstream of the line of abutment of the guide means 23 with the suction box end wall 3-1. The portion from the point y on the belt engaging surface downstream to the end wall 31 is primarily to facilitate connection of the guide means 23' to the end wall 31, and the radius in this relatively small portion is not particularly critical. It has, however, been emphasized that the radius between the points x and y is critical, and while it might be assumed that only a single radius measured from the point z in FIGURE 4 to a point midway between the points x and y is involved, actually there are two radii which must be controlled to overcome the entry and tensioniug problems mentioned. Thus, a line struck from the point a on the suction box end wall 31, and generally midway of the height of this wall, to the point b on the belt engaging surface produces what may be regarded as a tension control portion 23a-1 and an entry control portion 23a2. Exemplary radii for these two portions will be noted in the next paragraph, although it is believed now apparent that if the radius of the tension control portion 2311-1 as measured between the points x and b is too large, undue belt tensioning will result. On the other hand, if the radius for the entry control portion 23a-2 and measured from the point b to the point e is too small, belt flexing or whipping will likely result. It may accordingly be observed that the guide means 23 in accordance with this invention has a belt engaging surface 23a comprised of two curved connected portions 23a-1 and 23a2 having radii such that undue belt ten- :sion is prevented and the belt 22 smoothly transcends onto the suction box cover 35.

It has been found in practice that the radii discussed, one or both, depend upon certain variables. These variables are generally the length of the suction box 14, the length of the rotary belt 22 and the physical properties of the belt. Among the physical properties which must be considered are the belt stiffness, type of grooving 22c therein, type of punching 22a therein, type of reinforcing, belt thickness and rubber hardness. As a specific example, proper belt tension and entry were achieved when the radius of the tension control portion 23a-1 of the belt engaging surface 23a, as measured from the point In along the reference line mn was approximately three inches, and the radius of the entry control portion 2311-2 measured from the point a along the reference line a--b was fixe inches, when the overall length of the suction box 14 was about 32% inches and the inside circumferential length of the belt 22 was 82 inches. The radii mentioned were further achieved with a belt having a thickness of /8 inch, grooved and punched as disclosed, and being of moderate stiffness and hardness as utilized in the art.

The one first guide means 23 when constructed as described not only eliminates belt flexing upon entry onto the suction box cover 35 and effectively controls belt tension, but also together with the other first guide means 24 provides a fluid-tight header to supply a fluid such as Water through the passaged screw means 57 into the conduits 50 and through the passaged screw means 47 to the underside of the belt 22 to provide the necessary belt lubrication. Each guide means and header is attached by welding or related techniques to an adjacent side wall 31 or 32 of the suction box body portion 30, and each of the devices 23 and 24 is provided with opposed end walls 23b and 24b, one only of which is shown. There is in this manner provided a closed header, and defined therewithin is a fluid supply chamber 23c. As appears in FIG- URES 2 and 4, one or both of the end walls 23b and 24b of the guide means 23 and 24 is passaged at 23d and 24:1 to provide a connection for fluid supply conduits 23c and 242, diagrammatically indicated in FIGURE 2 and I connected to a source of liquid under pressure controllable by pump means or the like 62 and 63, also indicated diagrammatically. Of course the conduits 23c and 242 may be connected to a common line under control of a single pump, and valve means (not shown) would normally be employed in the manner customary in the art.

Guide means 23 and 24 having the controlled radii indicated are effective to prevent belt skewing caused by whipping or flexing of the belt upon entry onto the suction box cover. However, belts skewing can also be caused by unavoidable errors in belt manufacture, such that there are differences in the circumferential length of the belt on opposite sides thereof. It was stated in the introductory material hereto that in a belt having a circumferential length on the inside thereof of approximately fifteen feet, a difference in the length on the opposite sides of the belt may be of the order of of an inch or more. While this difference may seem inconsequential, it is of sufficient magnitude during successive revolutions of the belt to cause the short belt side to lead the long belt side, until utimately the belt skews relative to the suction box top, causing misalignment of the drain perforation 22a in the belt 22 and the drain perforation 42 in the suction box cover 35.

This can be seen in FIGURE 6, which portrays in somewhat exaggerated form the belt skewing problem. Like numerals from FIGURE 5 have been applied thereto, and in FIGURE 6 the relatively shorter side of the belt is designated as 22s and the relatively longer side as 221. It can be noted therefrom that when the rubber belt 22 is moving over the suction box cover 35 in the direction indicated by the arrow 43, and belt skewing occurs either from belt flexing at the oncoming side of the suction box 14 or by reason of unavoidable errors in manufacture causing the belt side 22: to be relatively shorter than the belt side 22!, certain of the drain perforations 22a in the belt 22 do not align themselves with the drain openings 42 in the suction box cover 35. Accordingly, in those areas where the desired hole alignment does not occur, poor dewatering of the web W can be anticipated. In addition, it is to be further observed from FIGURE 6 that in those areas where alignment of the belt perforations 22a and cover perforations 42 do not occur, the belt land areas 22b cover either partially or completely certain of the cover drain perforations 42. Since suction is constantly being drawn through the perforations 42 to the interior of the suction box 14, it can readily be appreciated that belt seizure may occur, and at least excessive belt drag will take place.

However, the noted problem of belt skewing by reason of differences in the belt length on opposite sides thereof is essentially entirely eliminated by provision of second guide means, constructed as indicated by the numeral 25 in FIGURES 1 and 2, or by use of the means to be later described in connection with FIGURES 8, 9 and 10. As appears in FIGURES 2 and 7, the second guide means 25 having a curvature such that the belt conforms substantially to its natural curvature in an untensioned state is within the loop of the endless belt 22 generally beneath the suction box 14. The second guide means 25 comprises a curvate or arcuate belt engaging portion essentially coextensive with the width of the belt 22 and having upwardly turned end portions 70a and 79/) to prevent interference with the travel of the belt 22. The belt engaging member 70 is desirably rigidified at transversely spaced locations by arcuate plate members 71 (FIGURE 7) welded or otherwise secured to the belt engaging member 70 and to a generally flat plate 72 suitably attached to the bottom wall 34 of the suction box body portion 30 and generally coextensive therewith. As also appears in FIGURE 7, the arcuate plate members 71 at opposite ends of the suction box body portion may be of somewhat reduced height, as compared with the arcuate plates intermediate the box ends, in order to effect a securement of the second guide means 25 to plate means 73 attached by bolt means 74 to the bottom Wall 34 of the suction box at locations spaced longitudinally therealong. As well, to rigidify the connection between the arcuate belt engaging member 70 and the plate means 73 bracket means 75 and 76 are provided. Desirably, welding techniques are employed to secure the reduced height bracket means 75 to the belt engaging member 70 and plate means 73, and a like mode of attachment used to secure the central and relatively greater height bracket means 76 to the elements mentioned.

The second guide means 25 may be seen from FIGURE 2 to be in relatively light engagement with the traveling belt 22 along essentially its entire lower run, and that the belt is unsupported along only a relativei short distance from adjacent the upwardly turned portions 742a and 70b of the belt engaging member 7% to the first guide means 23 and 24. By provision of the second guide means 25 the belt 22 is confined to a symmetrical shape by a restraining action, or as may otherwise be stated, the belt is forced to conform to its natural curvature in an untensioned state. By so restraining the lower belt run, the belt during travel along the suction box cover 35 moves with its longitudinal centerline aligned with the longitudinal centerline of the suction box cover. T hereby, the belt 22 is at all times maintained the desired distance from the guide means 49, there is no scraping of the belt thereagainst, and the condition portrayed in FIGURE 6 does not occur, but rather, the belt travels as shown in FIG- URE 5.

Other forms of guide means can be employed to restrain the lower belt run and to assure that the belt conforms substantially to its natural curvature in an untensioned state. Other forms of the invention are illustrated in FIGURES 8, 9 and reference being first made to FIGURE 8. The suction box 114- of FIGURE 8 can be constructed in the manner described in connection with FIGURES 2, 3 and 4, and as well, the first guide means 23 and 24 may be constituted as was also previously disclosed. Accordingly, like numerals have been applied thereto.

In the embodiment of FIGURE 8, there is located within the loop of the endless belt 22 and generally beneath the suction box 14 a pair of rolls 8t) and 31 which may or may not be driven. In any event, the lower belt run is effectively restrained and thereby confined to a symmetrical shape, so that uneven belt tracking does not occur when opposite sides of the belt are of different circumferential lengths. The rolls 8!} and 81 may not be only two in number, and it is within the contemplation of this invention that one or more rolls be spaced therebetween. In addition, while the rolls 80 and 81 may extend transversely in generally parallel relation to opposed side walls of the suction box 14, effective guiding action is also provided when the rolls are diagonally disposed relative to the direction of belt travel. Under these circumstances, adjacent ends of the rolls 8t) and 81 would overlap or be relatively close thereto. Further, and as was earlier stated, the rolls 80 and 81 may take the form of pipe means.

In FIGURE 9 the suction box 14 has the same configuration, and the first guide means are generally triangularly shaped and are indicated in this view by the numerals 82 and 83. Such guide means, and particularly the guide member 82 has a radius calculated to provide smooth transition for the belt 22 onto the suction box 14 to prevent belt flexure.

The embodiment of FIGURE 9 further incorporates therein rolls 84 and -85 at the oncoming and off-running sides of the box, and one or both of these rolls may be driven to cause belt travel. However, the rolls need not be driven, since as earlier indicated the endless belt 22 may be driven in rotation by the forming wire 11. Also within the belt loop is roll means 86, shown by the arrow 87 applied thereto to be tiltable in a vertical direction in order to not only effectively guide the belt 22, but to vary the tension therein due to differences in the circumferential length of the belt on opposite sides thereof. In other words, on the relatively shorter side of the belt 22, a relatively greater tension would be applied, and this may be accomplished by bearing structure well known to the art. The guide and tensioning means 86 may of course be responsive to changes in belt tension, and this may be accomplished by having the belt 22 along its lower run in contact with suitable detecting means actuating valve means and controlling the air supply thereto. The output of the valve means could then be readily fed to diaphragm means in control of the bearing means mounting the roll 86.

In the embodiment of FIGURE 10, the suction box 14 and first guide means 23 and 24 are constructed as earlier described in connection with FIGURES 2, 3 and 4, and like numerals have accordingly been applied thereto. The second guide means assuring that the belt 22 conforms substantially to its natural curvature in an untensioned state takes the form of roll means 88 tiltable horizontally in the directions indicated by the arrow 89 applied thereto. The roll means 88 can incorporate generally the bearing structure described in connection with FIGURE 9, and as well, such bearing means may be responsive to tension variations in the belt 2 2., to assure 10 that the loose or longer side of the belt will be properly tensioned to assure even tracking along the suction box cover.

It has been the prior practice in the art to shift the suction box relative to the direction of wire travel so as to align the belt center with the wire center. This procedure can be utilized in the instant invention, although experience to date has demonstrated that the first and second guide means described renders shifting of the suction box unnecessary in the majority of instances.

Various forms of first and second guide means for directing the endless belt along the suction box cover have been shown and described herein, and of course, the instant invention is susceptible of other changes and modifications therein without departing from the novel concepts thereof.

We claim as our invention:

1. In a dewatering apparatus including a suction device, a drain band trained thereover, and a looped carrier band supporting the drain band over the suction device, the improvement of guide means within the loop of the carrier band generally beneath the suction device and having a curvature such that the carrier band conforms substantially to its curvature in an untensioned state.

2. In a paper machine which includes a suction box receiving thereover an endless flexible belt in supporting contact with a traveling forming wire, and first guide means providing a curved surface at the oncoming side of the suction box and having a radius such that the belt is properly tensioned and smoothly transcends onto the top of the suction box Without rising therefrom, the improvement which comprises second guide means within the loop of the endless belt having a stationary arcuate surface contacting the belt and restraining the same to confine the belt to a symmetrical shape.

3. In a paper machine which includes a suction box receiving thereover an endless flexible belt in supporting contact with a traveling forming wire, the improvement which comprises guide means for supporting the belt at the ends of the suction box, at least one of said guide means providing a complex non-planar surface, said surface having lower and upper portions each having a different radius of curvature, said lower portion having a shorter radius of curvature than the upper portion so that the belt smoothly transcends along said surface.

4. A paper machine in accordance with claim 3 wherein the guide means at both ends of the suction box have the same shaped surface and each of the surfaces is shaped with a lower and upper portion of different radii of curvature with the lower portion having a shorter radius than the upper portion so that the belt smoothly transcends along said surfaces onto the top of the suction box and off of the top of the suction box.

5. In a paper machine which includes a suction box receiving thereover an endless flexible belt in supporting contact with a traveling forming wire, the improvement which comprises guide means for supporting the belt at the ends of the suction box with at least one of said guide means having a complex curved convex continuously smooth surface shaped so that the belt smoothly transcends along said surface.

6. A paper machine constructed in accordance with claim 5 wherein the surface of the guide means positioned ahead of the suction box on the oncoming side thereof is shaped in accordance with claim 5 being complex curved and convex so that the belt smoothly transcends along the surface and onto the top of the box.

7. In a paper machine which includes a suction box receiving thereover an endless flexible belt in supporting contact with a traveling forming wire and first guide means on the oncoming side of the suction box guiding the belt onto the top of the box, the improvement which comprises second stationary guide means below the suction box having a non-moving sliding belt-engaging arcuate surface for guiding the lower run of the belt.

8. In a paper machine which includes a suction box suction box having a non-moving sliding belt-engaging receiving thereover an endless flexible belt in supporting arcuate surface for guiding the lower run of the belt. contact with a traveling forming wire, the combination comprising first guide means at the oncoming side of Referen e Cited in th file f thi patent the suction box having a complex curved convex con- 5 tinuously smooth surface shaped so that the belt smoothly UNITED STATES PATENTS transcends along said surface and onto the top of the 2,981,328 Justus P 1961 box, and a second stationary guide means below the 2,981,329 Justus P 1961 

8. IN A PAPER MACHINE WHICH INCLUDES A SUCTION BOX RECEIVING THEREOVER AN ENDLESS FLEXIBLE BELT IN SUPPORTING CONTACT WITH A TRAVELING FORMING WIRE, THE COMBINATION COMPRISING FIRST GUIDE MEANS AT THE ONCOMING SIDE OF THE SUCTION BOX HAVING A COMPLEX CURVED CONVEX CONTINUOUSLY SMOOTH SURFACE SHAPED SO THAT THE BELT SMOOTHLY TRANSCENDS ALONG SAID SURFACE AND ONTO THE TOP OF THE BOX, AND A SECOND STATIONARY GUIDE MEANS BELOW THE SUCTION BOX HAVING A NON-MOVING SLIDING BELT-ENGAGING ARCUATE SURFACE FOR GUIDING THE LOWER RUN OF THE BELT. 